During surgery, it is often necessary to temporarily occlude blood flow through certain vessels to prevent leakage of blood through incisions made distal to the surgical site. Various devices and techniques exist for accomplishing temporary occlusion, including application of external surgical clamps to the vessels to be occluded. External surgical clamps are available in many shapes and sizes, with varying characteristics. Prior art clamps exist which are connected to elongated arms controlled by handles, such that a surgeon can apply and remove the clamp from outside the operating site. See for example U.S. Pat. No. 5,133,724 to Wilson, Jr. et. al, and U.S. Pat. No. 5,447,515 to Robicsek. A drawback of these clamps, however, is that once they are applied, the arms and handles remain in place and may hinder the surgeon's access to the operating site. Other clamp and clamp appliers exist which allow the surgeon to apply the clamp and then withdraw the clamp applier. See for example U.S. Pat. No. 5,282,812 to Suarez, Jr. But once these clamps are applied, if the surgeon opts to loosen the clamp he or she must determine and apply the appropriate amount of force by hand. Still other clamps and clamp appliers designed for tissue manipulation exist that utilize tethers for retracting tissue from an operating site. See for example U.S. Pat. No. 5,304,183 to Gourlay et. al. This system, however, requires the use of more than one instrument and therefore may require multiple entries into the operating subject, and may also result in multiple instruments potentially obstructing the surgeon's access and or view to the operating site.
With the advent of endoscopic surgery, devices have been designed to allow a surgeon to apply a clamp through a trocar sleeve, then remove the clamp applier from the trocar sleeve to make the trocar available for introducing other surgical instruments or clamps. See for example U.S. Pat. No. 5,368,600 to Failla et. al, and U.S. Pat. No. 5,569,274 to Rapacki et. al. A primary feature of the Failla invention is the ability of the surgeon to steer the clamp to the desired location by means at the proximal end of the applier. A primary feature of the Rapacki invention is the fact that the clamp is held by the applier at a single engagement point. Both of these inventions appear to solve the problem of having access obstructed by the applier; however, they both require the surgeon to use two hands to effectively manipulate the clamp. Furthermore, the clamps disclosed in the Failla and Rapacki patents exert a predetermined amount of pressure on the clamped vessel based on the natural biasing of the jaws of the clamps.